1. Field of the Invention
The present invention relates to an oil pump system of a hybrid vehicle and a method for controlling the same, and more particularly, to an oil pump system of a hybrid vehicle which is provided to supply hydraulic pressure to a transmission using only an electric oil pump, and a method for controlling the same.
2. Description of Related Art
As well known, a hybrid vehicle uses both an engine and a battery power source. That is, the hybrid vehicle efficiently combines power of the engine and power of a motor, and uses the combined power.
An automatic transmission is typically mounted in the hybrid vehicle, and in order to supply operating hydraulic pressure to the automatic transmission, an oil pump system, which uses both a mechanical oil pump (MOP) and an electric oil pump (EOP), is mainly used.
The mechanical oil pump is driven by power of the engine so as to supply oil to the automatic transmission. Therefore, when an operation of the engine stops, the mechanical oil pump also stops such that oil is not supplied. Thus, the electric oil pump, which is driven separately from the engine, is mounted. For example, an oil pump system of a hybrid vehicle in the related art divides a section into a stop section, a low speed section, and a high speed section in accordance with a running state (speed) of the hybrid vehicle, and a method for controlling the oil pump may be performed by operating only the electric oil pump in the stop section, simultaneously operating the mechanical oil pump and the electric oil pump in the low speed section, and operating only the mechanical oil pump in the high speed section. That is, the electric oil pump of the oil pump system in the related art is used to supplement insufficient operating hydraulic pressure of the mechanical oil pump.
Because the mechanical oil pump is operated at all times when the engine starts, an unnecessary power loss may be caused, thereby degrading fuel efficiency. In addition, when the mechanical oil pump and the electric oil pump are simultaneously used, production costs may be increased.
Therefore, it is necessary to eliminate the mechanical oil pump, and a method of supplying oil to the automatic transmission by solely driving the electric oil pump is required.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.